Shaft bearing



June 19, 1928.

W aw w w m Lou/IJSFB scopes and theodolites, etc.

Patented June 19, 1928.

Louis F. BUFF, or' Jamaica snem, itIAssCHUSET si-mr'i' BEABING.

Appneation fiiea March 24, 1925. Vs'r'iai No. 17,817.

This invention relates to b'ea'rings` fo'r shafts and aims to providel an improved bearing` particularlyv adapted for instruments of precision such as trans'its, tele-v In the drawing of the particular embodiment of my invention illustrated and deseribed herein,

Figll is a side elevation pa'rtlyV in section for elearness; and V I Fig. 2 is a Vertical cross-section on vth line 2-2, F ig. 1. a

Referring to Fig. V1, my 'novel bearing comprises a lower member 1, of suitable size,

' commonlv the top of the standard, and a top or cap member2 therefor.

In instruments of this nature, ob'viously perfection of workmanship and accui'acy in use and results are the all in'ip'ortant Aobjects to be sou'ght. Accuraey to even l/'Oth of l/lOOOth of an inch is demanded and every feature of construction conducive to accurate results is Very necessary.

It is also not only desirable, but necessary,

' in using instruments of this type to have the telescope bearing so close a fit that the instrument, not shown, will remain'in position after adjustment and permit transportation and moving of the same, and also provide security against movement by the wind 01' reasonably slightl vibration from any cause. 'To obtain this close fit required for stability of the telescope, it will be clear that the fit between the bearing and shaft ends must be very accurate, as little or no lubrication can be used. Consequently and necessarily the degree of wear in such cases is large as compared with cases where free lubrication is provided for. o

To reduce the amount of wear to as low a point as possible, have conceived the plan of cutting away parts of the bearings in both the upper and lower members, leaving' very shallow arcuate spaces 3, 4, 5 between,v the bearing l and shaft 9, and perinitting' the shaft to ride on spaced sections or arcuate bearings 6, 7, 8. Naturally the lower side of the shaft 9 at its end and opposite recess 5 will ordinarily' receive the most wear due to the weight of the telescope, and this is avoided and the wear distributed more evenly between the arcuate bearings 7, 8 by providing' the recess 5. Really no bearing' member is necessary at 6 except to protect the shaft end from all danger of dislodgement from the member 1 during handling and ,t-ransportation, and to en's'uref close` working lit between the shaft and arcuate` bea'rings 7, 8.

It is desira'ble, liowever, to have at all times a Constant slight pressure 'Jon the shaft by the member 2 for the purp'ose of produeing al tight fit between the shaftand its-bearings, and thus ensure,'accuracy of movement of the telescope, and uniformity of wear in the b'earings so as practicable, and to permit moving Vand transporta- I tion of the instrument.

These objects I attain by pfrovidingV the member-2 withsef'ew's 1'0 threaded into the upper face ofthe `member l', and-pro'vided with a shouldferV 11, which is setup 'firm'l against the member 1; w i

,The., member 2 isl preferably ,provided with recess'pes12 to' receive the szcrewv heads' 13 ,and also'A a spring'v 14, one ,end o'f which seats against the'rcfew hje'atl 13, while the' opposite end seats agaiiis't'the slfro'u'lder 11 in the recess 12. This construction provides for a uniform and continued pressure b-y the member 2 on the shaft 9, taking up automatically and promptly fall looseness between the parts. This uniform pressure provides the friction necessary to maintain the shaft and its telescope in position against reasonable force, permits safe transportation and avoids necessity for frequent readjustment. Theshoulders provide a positive and firm seat for the screws and a positioning of the member 2 with the maximum clearance of l/Gtth of an inch for future adjustment, and help in securing continued equal pressure throughout the bearing ares and thus prevent inaccuracy of adjustment from unequal Wear of parts which follows the present use of set screws individually set up to hold member 2 on member 1, and'which are seldom if'everturned up to the same extent. By taking up the wear as it occurs, moreover, dust is prevented from getting access to the clearance between the parts.

The nature of the use of a transit is such that for' most of the adj ustments of the telescope, it is only moved a short distance from the horizontal. This use results in more uneven wear of the bearings than would be the case if the telescope were frequently turned through a complete circle. Hence, when the telescope, is turned through a complete Circle and reversed, as in triangulation work, the uneven bearing or looseness,

if not prevented by automatic action of the spring 14, becomes more apparent and results in inaccuracy which it is most desirable to aVoid. This is avoided largely by my construction because the looseness is constantly being taken up.

Of course the accuracy of the adjustinent of the member 2 relative to the member 1 depends largely upon the uniformity of the temper 'of the spring 14. Usually this can be obtained. Sometimes, however, it is impossible to secure eXact uniformity. In such case, the screw carrying the strongest spring` must be backed off or unscrewed a little so that the two ends of the member 2 will be, equi-distant from 'the member 1. f Or, sometimes, afterV long use, one spring` loses part of its strength and allows its end of the member 2 to rise from the member 1 further than it should. Then. either the screw carrying the Stronger spring must be backed off or a new spring substituted for the weak one, and if the instrument is being used in the field, this is usually impossible. Therefore, in either ofthe above cases, when one of the screws is backed off so that its shoulder does not seat against the member 1,then results the possibility of the screw workingV loose With the consequent uneven positioning of the two ends of the member 2.

Lem-,817

To guard against, this danger, I have conceived the idea of using a compensating cise embodiment thereof illustrated and described herein, andl I claim: 'A shaft bearing for instruments of preclslon and the llke comprlsing a lower member, bored and counterbored to re'ceiiie a screw and a screw looking spring thereunder; an 'upper member bored and counterbored to receive ascrew and'a spring thereabout; a shouldered screw seated at its shoulder on the lower member with a spring seated in the counterbore and yieldingly engaging the lower end of the screw, and a spring seated in the counterbore of the upper member and yieldingly engaging the screw-head whercby the screw is positively seated in the lower member, and the upper member is yieldingly held upon the shaft.

In testimony whereof, Ihave signed my name to this specification.

LOUIS F. BUFF. 

